Avian pathogenic Escherichia coli ( APEC ) causes extensive mortality in poultry flocks, leading to extensive economic losses. The aim of this study was to investigate the phenotypic and genotypic characteristics and antimicrobial resistance of recent APEC isolates. Of the 79 APEC isolates, the most predominant serogroup was O78 (16 isolates, 20.3%), followed by O2 (7 isolates, 8.9%) and O53 (7 isolates, 8.9%). Thirty-seven (46.8%) and six (7.6%) of the isolates belonged to phylogenetic groups D and B2, respectively, and presented as virulent extraintestinal E. coli . Among 5 analyzed virulence genes, the highest frequency was observed in hlyF (74 isolates, 93.7%), followed by iutA (72 isolates, 91.9%) gene. The distribution of the iss gene was significantly different between groups A/B1 and B2/D ( P < 0.05). All group B2 isolates carried all 5 virulence genes. APEC isolates showed high resistance to ampicillin (83.5%), nalidixic acid (65.8%), tetracycline (64.6%), cephalothin (46.8%), and ciprofloxacin (46.8%). The β-lactamases–encoding genes bla TEM-1 (23 isolates, 29.1%), bla CTX-M-1 (4 isolates, 5.1%), and bla CTX-M-15 (3 isolates, 3.8%); the aminoglycoside-modifying enzyme gene aac(3)-II (4 isolates, 5.1%); and the plasmid-mediated quinolone genes qnrA (10 isolates, 12.7%) and qnrS (2 isolates, 2.5%) were identified in APEC isolates. The tetA (37 isolates, 46.8%) and sul2 (20 isolates, 25.3%) were the most prevalent among tetracycline and sulfonamide resistant isolates, respectively. This study indicates that APEC isolates harbor a variety of virulence and resistance genes; such genes are often associated with plasmids that facilitate their transmission between bacteria and should be continuously monitored to track APEC transmission in poultry farms.

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Genes encoding ciprofloxacin resistance in enterococci in animals may be transferred to bacteria in the animal gut and to zoonotic bacteria where they could pose a human health hazard. The objective of this study was to characterize antimicrobial resistance in high-level ciprofloxacin-resistant (HLCR) Enterococcus faecalis and Enterococcus faecium isolated from retail chicken meat. A total of 345 enterococci (335 E. faecalis and 10 E. faecium) were isolated from 200 chicken meat samples. Of these, 85 E. faecalis isolates and 1 E. faecium isolate were confirmed as HLCR enterococci. All 86 HLCR enterococci displayed gyrA- parC point mutations consisting of S83I-S80I (94.2%, 81 isolates), S83F-S80I (2.3%, 2 isolates), S83Y-S80I (2.3%, 2 isolates), and S83Y-S80F (1.2%, 1 isolate). Sixty-one (72.9%) of the 86 HLCR enterococci showed multidrug resistance to three to six classes of antimicrobial agents. Multilocus sequence typing revealed that E. faecalis had 17 different sequence types (ST) and E. faecium had 1 different ST, with ST256 observed most often (44 isolates, 51.8%). Although these results cannot exclude the possibility that pathotypes of enterococci isolated from chicken might represent transmission to or from humans, the foodborne HLCR E. faecalis indicated that the food chain is a potential route of enterococcal infection in humans.

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Vertical integration of the broiler industry allows producers to combine different biosecurity and sanitation practices, housing technologies, and feeding regimens to improve food safety. The objectives of this study were to determine the antimicrobial resistance pattern of β-lactamase-producing E. coli and to compare the characteristics of E. coli recovered from 7 different integrated broiler operations in South Korea. Among 200 chicken meat samples, 101 were observed to be positive for E. coli. However, the prevalence varied from 37.5% to 75.0% in chicken meats from different operations, indicating variation in E. coli occurrence among the operations. Among 101 isolated E. coli from chicken meat, 59 were identified third-generation cephalosporin-resistant E. coli and recovered from 7 different operations. A high proportion of the E. coli isolates were resistant to penicillins (89.8%), quinolones (81.4%). Among 59 third-generation cephalosporin-resistant E. coli isolates, 29 showed phenotypic and genotypic characteristics of β-lactamase-producing E. coli. Prevalence of bla gene, blaCTX-M-1, blaCTX-M-14, blaCMY-2, and blaTEM-1, were identified in 2, 4, 8, and 16 E. coli isolates respectively and only one E. coli had both genes, blaTEM-1 and blaCTX-M-1. Pulsed-field gel electrophoresis (PFGE) analysis was performed on 29 β-lactamase-producing E. coli isolates. In PFGE, E. coli included 7 PFGE patterns showing the same operation and an accorded both resistance to β-lactam antibiotics and presence of the bla-gene. Our findings suggest that E. coli with resistance to third-generation cephalosporins can now be found in association with integrated broiler operations, providing the data to support the development of monitoring and preventing program in integrated operations.